I removed the water pump and the breather tube, then spent half an hour scrubbing rust, scale, and paint off the exterior. I gave it a good blasting with the power washer, dried it with compressed air, and then set to masking and painting.
Two coats of primer, two coats of semi-gloss black engine enamel. I'll let it cure overnight.
I'm thinking that I'll also clean up and paint the engine bracketry and valve cover, just to make it look extra keen.
...then bolt it up to a crummy-looking transmission. *sigh* Well, the transmission won't be too visible....